One of the London Bridge knifemen had been reported to the anti-terror police over fears he was attempting to radicalise schoolchildren, according to reports.

The suspect was reportedly said to have become radicalised after watching extremist videos on YouTube.

People (right) lie on the ground after being detained by police at Elizabeth Fry flats in Barking, east London. Picture: PA

Residents at the Elizabeth Fry flats in King’s Road, Barking - where a number of arrests were made on Sunday - said they recognised the attacker from a photograph and said he was of middle-eastern or Pakistani origin, had children, and had lived in the area for a number of years.

According to The Times, the Barking suspect, in his 20s, had preached to people at his flat, worked on the transport network and worked for a few hours a week at an Islamic fitness centre where he also took part in boxing and taekwondo.

Housewife Erica Gasparri, 42, told The Times she had reported the suspect to police last year after challenging him in a park near a school.

She said: “They were waiting for the children of the neighbourhood. They would give the children chocolate while talking to them. They would pray in the park for hours.”

A friend told the BBC Asian Network he had reported him to the anti-terror hotline after he began expressing increasingly radical views and justifying terror attacks, but the friend said he was never arrested.

The Daily Mail reported the suspect had featured in the Channel 4 documentary The Jihadis Next Door, which filmed alleged extremists.

Salaudeen Jailabdeen, 40, who lives in a neighbouring block of flats, said the suspect had once been ejected from a local mosque for interrupting an imam.